JPH08186719A - Communication equipment - Google Patents

Abstract

PURPOSE: To provide a communication equipment provided with a function for deciding the position of an adaptive template picture element based on cycle information when a correlation cycle among picture elements is known. CONSTITUTION: A facsimile equipment binarizes picture data read in a read part 1 in a picture processing part 2, encodes them in an encoding/decoding device 6, outputs them through a modem 7 and an NCU 8 to a telephone line and transmits them to a reception. side. Prior to encoding at the time of transmission, the number of picture elements in horizontal direction and vertical direction for expressing the correlation cycle among the picture elements is inputted from an operation part 9, the position of the adaptive template picture element to an encoding object picture element is changed within a prescribed range including an input value, the picture data are encoded at the respective positions and a compressibility is calculated. The position which supplies the highest compressibility among them is defined as the position of the adaptive template picture element in the encoding at the time of the transmission.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device such as a facsimile, an electronic copying machine having a data transmission function and an image scanner, and more particularly to encoding of transmitted image data.

[0002]

2. Description of the Related Art In facsimiles, which are now widely used, binary (0/1, L level / H level, etc.) image data is transmitted. Further, binarized image data is also handled in an electronic copying machine, and recently binarized image data is stored in a storage device such as a magnetic disk and can be read out to reproduce an image as needed. It is supposed to be. In recent years, along with the diversification of image data, there has been an increasing demand for higher resolution of images, that is, higher density of the number of pixels, and the amount of data to be transmitted or stored is inevitably huge.

In order to efficiently transmit image data, 2
The value-coded data is encoded and compressed, and as its method, the modified Huffman (MH), modified read (MR), and modified / modified read (MMR) methods have been standardized and put into practical use. In these encoding methods, sequential buildup is performed in which binary data is encoded in the order in which the original image is scanned and read. In sequential build-up, like a facsimile, the sending device scans the paper surface of the document from left to right from top to bottom and transmits, and the receiving device decodes in the order received and reproduces the image on the paper surface. This is convenient because it is not necessary to store the received data in the receiving side device.

On the other hand, a high resolution image is not always required, and it may be necessary to quickly transmit and reproduce the entire image even with a rough quality. However, it is not easy to sufficiently deal with this in the above sequential buildup. For this reason, progressive build-up, in which coarse image data is first transmitted, and additional data is added as necessary to gradually increase the resolution of a reproduced image, has been receiving attention. Furthermore, there is an increasing demand for high-speed and faithful reproduction of halftone images.

Under such circumstances, JBIG (Joint Bi-l
evel Image Coding Experts Group) was established to study efficient coding of binary data. In JBIG, the main issues are parallelization of progressive build-up and sequential build-up, high data compression effect, information storability, and high-speed processing.
The base system of value data encoding is adopted.

First, a progressive build-up hierarchical image (images having different resolutions) is created by image reduction. Next, a pixel whose value is inevitably determined, that is, a pixel which does not need to be encoded is found from pixels whose values are known. This is performed in two steps, for example, a line in which all pixels are blank, in which the pixel value is determined irrespective of the image reduction method, and a line in which the pixel value is determined depending on the image reduction method. The former is a typical prediction and the latter is a definitive prediction. This reduces the number of pixels to be encoded. For the pixels remaining as the encoding target, arithmetic encoding is performed with reference to a pixel group called a template. A method called a QM coder is adopted for arithmetic coding.

A model template and an adaptive template (AT) are used as templates to be referred to when encoding a pixel to be encoded (hereinafter also simply referred to as an encoded pixel).
There is. The model template is a set of coded pixels located in the vicinity of the coded pixels, and the number of pixels forming the model template and the positional relationship with the coded pixels are defined. For example, the image of the lowest resolution layer in the progressive build-up includes two lines of 9 pixels shown by M in FIG. 8 and 9 lines shown by M in FIG.
The one with three lines of pixels is used. In both figures, C is a coded pixel. For higher resolution layers,
Other model templates having different numbers of constituent pixels are prepared. In sequential build-up, there is only one hierarchy and the model template of Figures 8 and 9 is used.

On the other hand, the adaptive template does not have a fixed positional relationship with respect to the coded pixels, but the position can be set according to the image. The default position of the adaptive template in the lowest resolution layer image is shown in FIGS. 8 and 9. The adaptive template aims to improve the coding efficiency for an image having a periodic correlation between pixels, and is selected in consideration of the correlation of pixels. In particular, it is used for an image having a strong correlation in a pixel value at a constant cycle, such as a dither image obtained by binarizing an image of a halftone with a predetermined threshold value, to improve coding efficiency.

In FIGS. 8 and 9, x and y are coordinate axes when the coded pixel C is the origin, and the arrow x indicates the front in the main scanning direction and the arrow y indicates the rear in the sub scanning direction. As the encoding progresses, the encoded pixel moves by one pixel in the main scanning direction, and the pixel positions of the model template and the adaptive template also move by one pixel accordingly.
The relative position of the template with respect to the coded pixel is kept constant except for the peripheral area of the image. For the coded pixels existing in the peripheral area of the image data, the relative positions of the model template and the adaptive template cannot be kept constant, but an exception is defined separately for this.

The selection of the model template and the determination of the position of the adaptive template with respect to the coded pixel are
It is performed according to the image transmitted by the transmitting side. The selected model template and adaptive template position are described in the header along with other information used for encoding,
It is sent before the image data. The receiving side decodes the encoded image data based on the information written in the header. Therefore, the image data obtained by scanning and reading the original on the transmitting side is surely reproduced on the receiving side.

The compression rate of image data can be expressed by various methods, but the most general expression is expressed by the equation (1).
Expression (1) represents the size of the image data after encoding with respect to the size of the image data before encoding, and the smaller the value, the higher the compression rate.

[0012]

[Equation 1]

CCITT (International Telegraph and Telephone Consultative Committee) No. When one original image is encoded, MH, MR, MM
In the R and JBIG systems, 0.14 and 0.1, respectively.
Compression ratios of 3, 0.035 and 0.028 have been obtained. The original document image is image data composed of characters, tables, graphs, etc., and is compressed well by any method. However, the former three methods are not intended for the image data of the intermediate gradation, so that the compression efficiency is significantly reduced for such image data, and the compression rate becomes 1 or more and the reverse It is known that the amount of data increases. On the other hand, the JBIG method is expected to achieve good compression with a compression rate of about 0.1 even for image data of halftone.

[0014]

As described above, the adaptive template is referred to in order to efficiently encode and compress an image having a periodic correlation between pixels. In JBIG, the adaptive template pixel exists. Although it defines the range, it does not give instructions on how to determine the position of the adaptive template pixel. Further, there is no conventional technique showing a method of determining the adaptive template pixel position.

For the purpose of the adaptive template, it is important to use a pixel having a high correlation with the coded pixel. When the adaptive template is a pixel having a low correlation with the coded pixel, the coding efficiency is lowered and the compression rate is also lowered. On the other hand, when it takes a long time to determine the position of the adaptive template, even if the coding efficiency is improved, the efficiency of the entire transmission of the image data may be lowered.

It is an object of the present invention to provide a communication device which has a function of determining the position of an adaptive template pixel based on the period information when the correlation period between pixels is known, and which enables efficient coding. To do.

[0017]

In order to achieve the above object, according to the present invention, an input means for inputting the position of an adaptive template pixel in a communication device for encoding image data according to the JBIG encoding method, Compression rate calculating means for calculating the compression rate by encoding by comparing the size of the image data before encoding and the size of the image data after encoding,
The position of the adaptive template pixel is changed within a predetermined range including the position input from the input unit, the image data is encoded at each position, the compression ratio is calculated by the compression ratio calculation unit, and the highest compression ratio is obtained. Position determining means for determining the position of the given adaptive template pixel,
Coding means for coding the image data with reference to the adaptive template pixel whose position has been determined by the position determining means.

Further, in a communication device for transmitting image data composed of binarized pixels by sequentially encoding the values of the respective pixels, the number of horizontal pixels and the number of vertical pixels are input. Input means, an encoding means for sequentially encoding the encoding target pixels by referring to a reference pixel at a predetermined relative position with respect to the encoding target pixel, and encoding the image data; A compression rate calculating unit that compares the size of the image data and the size of the image data after encoding to calculate the compression rate by encoding, and the relative position of the reference pixel with respect to the pixel to be encoded is the pixel in the horizontal direction in the horizontal direction. Number within a range of a first predetermined number of pixels, and each horizontal position is changed in the vertical direction within a range of a second predetermined number of pixels including the number of pixels in the vertical direction. Image data And a reference pixel position determining means for determining the position that gives the highest compression ratio and determining this position as the relative position of the reference pixel with respect to the pixel to be coded. The configuration is provided.

Specifically, the above configuration is realized in a facsimile machine.

Further, an original reading means, an image processing means for processing the image data read by the original reading means and giving the image data to the encoding means, and the image data encoded by the encoding means to the storage device. The above configuration may be realized in a copying machine and an image scanner that include a transmitting unit that transmits.

[0021]

In a communication device for encoding image data according to the JBIG encoding method, the input means for inputting the position of the adaptive template pixel and the size of the image data before encoding and the image data after encoding are compared. Then, the compression rate calculating means for calculating the compression rate by encoding and the position of the adaptive template pixel are changed within a predetermined range including the position input from the input means, and the image data is encoded at each position. The image data is coded with reference to the position determining unit that determines the position of the adaptive template pixel that gives the highest compression ratio by the compression ratio calculating unit and the adaptive template pixel whose position is determined by the position determining unit. When it is configured to include encoding means for encoding, it is located within a predetermined range including the input position. For Dapu Restorative template pixel respectively, encoding of image data is performed, the compression ratio is calculated. The position corresponding to the highest compression ratio among these is referred to by the encoding means as the position of the adaptive template pixel, and the image data is encoded.

The period of correlation between pixels is known.
When the number of pixels per cycle is input as the position of the adaptive template pixel, the compression rate due to the coding at that position becomes the highest. When the number of pixels close to the correlation period is input, the number of pixels corresponding to the correlation period exists within a predetermined range, and the coding at this position gives the highest compression rate. The adaptive template pixel position that matches the correlation period of the image data after reading must be within the specified range even if there is some error in reading the image of the document, such as when the document is tilted. Which gives the highest compression ratio.

Further, even when the period of correlation between pixels is not known, the adaptive template pixel position that gives the highest compression ratio within a predetermined range including the input position is determined and used for encoding.

In addition, in a communication device for transmitting image data composed of binarized pixels by sequentially encoding the values of each pixel, the number of horizontal pixels and the number of vertical pixels are input. Input means, an encoding means for sequentially encoding the encoding target pixels by referring to a reference pixel at a predetermined relative position with respect to the encoding target pixel, and encoding the image data; A compression rate calculating unit that compares the size of the image data and the size of the image data after encoding to calculate the compression rate by encoding, and the relative position of the reference pixel with respect to the pixel to be encoded is the pixel in the horizontal direction in the horizontal direction. Number within a range of a first predetermined number of pixels, and each horizontal position is changed in the vertical direction within a range of a second predetermined number of pixels including the number of pixels in the vertical direction. Image data And a reference pixel position determining means for determining the position that gives the highest compression ratio and determining this position as the relative position of the reference pixel with respect to the pixel to be coded. When the configuration is provided, the relative position of the reference pixel with respect to the pixel to be encoded is changed within the range of a predetermined number of pixels in the horizontal direction and the vertical direction, and the compression is calculated for each. At this time, the range of change of the reference pixel position includes the number of input pixels in both the horizontal and vertical directions. Of all the reference pixel positions within the predetermined range, the one that gives the highest compression rate is determined as the relative position of the reference pixel with respect to the pixel to be encoded.

The correlation period of pixels is known, and when the number of pixels corresponding to one period in each of the horizontal direction and the vertical direction is input from the input means, a pixel located at a position separated from the encoded pixel by the number of input pixels is selected. The reference pixel gives the highest compression ratio. When the number of pixels in the horizontal and vertical directions close to the correlation cycle is input, the relative position corresponding to the correlation cycle exists within the predetermined range, and the one with that as the reference pixel position has the highest compression rate. give. Even if there is some error in reading the original image, such as when the original is set to be tilted, the relative position where the number of pixels is close to the horizontal and vertical correlation periods of the image data after reading It exists within a predetermined range, which gives a high compression rate.

Further, even when the period of correlation between pixels is unknown, a reference pixel position giving the highest compression ratio is found within a predetermined range including the number of input pixels,
This is determined as the relative position with respect to the pixel to be encoded.

When the above configuration is realized in a facsimile apparatus, the probability that a pixel referred to at the time of encoding correlates with the pixel to be encoded when the correlation period is known is high. Moreover, the compression ratio is actually calculated and confirmed,
Encoding is performed so as to obtain the highest compression rate. Therefore, the transmission time of the image data of the facsimile apparatus is shortened. Even when the correlation period is not known, the pixel that gives the highest compression ratio within the predetermined range is referred to, so that the coding efficiency is improved.

Further, an original reading means, an image processing means for processing the image data read by the original reading means and giving the image data to the encoding means, and the image data encoded by the encoding means to the storage device. When the above-described configuration is realized in a copying machine and an image scanner including a transmitting unit for transmitting, image data read by the document reading unit and processed by the image processing unit has a high probability of being correlated when the correlation cycle is known. Encoding is performed by referring to the pixel to be processed. Moreover, since the compression rate is actually calculated and confirmed, and the encoding is performed so as to obtain the highest compression rate, the image data is reliably and efficiently compressed. Therefore, the transmission time from the transmission means of the copying machine and the image scanner to the storage device is shortened, and the amount of data stored in the storage device is reduced.
Even when the correlation period is not known, the pixel that gives the highest compression ratio within the predetermined range based on the input is referred to, so that the coding efficiency is improved.

[0029]

1 is a block diagram showing the configuration of a first embodiment in which the present invention is applied to a facsimile. The facsimile apparatus according to the present exemplary embodiment includes a reading unit 1 that reads a document image, an image processing unit 2 that processes image data output from the reading unit 1, a control unit 3 that controls the entire apparatus, and a ROM 4 that stores a control program and the like. RAM for temporarily storing image data, etc.
5, encoding / decoding device 6 for encoding and decoding image data, modem 7 for modulating and demodulating encoded image data, N for connecting to a telephone line and transmitting data
It has a CU (network control unit) 8, an operation unit 9 for a user to give an instruction to the control unit 3, and a recording unit 10 for outputting image data on a recording sheet.

The reading unit 1 is equipped with a light source and a CCD (charge coupled device). The original image is read by irradiating the original image with light from the light source and detecting the reflected light with the CCD.
The image is read by repeating scanning in the horizontal direction (main scanning) in the vertical direction at a predetermined pitch (sub scanning). CC
D outputs the detected light as an analog signal for each pixel.

The image processing unit 2 performs shading processing such as correction on the analog output from the CCD of the reading unit 1 due to variations in the sensitivity of the CCD, and then compares the image data with a predetermined threshold value for each pixel. Binarize to. Further, it has two types of dither matrices, and when binarizing an image of an intermediate gradation, dither processing is performed using these matrices.

In addition to the apparatus control program, the ROM 4 stores various tables including programs and model templates for performing various JBIG processes shown in FIG. The RAM 5 stores and holds the image data binarized by the image processing unit 2 until transmission, and also temporarily stores various calculation results performed by the control unit 3. Also, the received image data is stored and held. The encoding / decoding device 6 receives the image data for transmission,
Arithmetic coding is performed by the QM coder. For the received image data, the encoded image data is decoded in the reverse procedure to reproduce the image. Modem 7 and N
The CU 8 transmits and receives image data by a known standard method.

The control unit 3 is composed of a microcomputer, and reads a program stored in the ROM 4 to control the entire facsimile apparatus. Moreover, the position of the adaptive template pixel referred to at the time of encoding is determined. The control unit 3 includes a timer circuit 11 for timer transmission that transmits image data at a time designated by the user.

FIG. 2 shows a partial external view of the operation section 9. The operation unit 9 is a numeric keypad 5 for inputting a numerical value such as a facsimile number.
1, a start key 52 for instructing the start of reading an original, a stop key 53 for instructing to stop the operation, a memory print key 54 for instructing the output of the received data held in the RAM 5 by the recording unit 10, a start of designation of the transmission time Together with various keys such as the timer key 55 to indicate the
It has a display panel 56 made of D (liquid crystal display device).

The destination facsimile number input from the ten keys 51 is displayed on the display panel 56 and can be confirmed. If there is an error in the entered number, the cursor key 57 is used to move the cursor on the display panel 56 to that digit, the numeric keypad 51 is used to re-enter a number, and the setting key 58 is used to confirm. When performing timer transmission, the timer key 55 is operated and then the transmission time is input from the ten keys 51. The input transmission time is displayed on the display panel 56, and can be changed by operating the cursor key 57 or the like, like the facsimile number. The display panel 56 also displays a simple message regarding the operation to assist the user in the input operation.

The operation section 9 includes a status display section 59 for displaying the status of the apparatus, a density specification section 60 for instructing the image density of the original, and an image quality specification section 6 for instructing the image quality of the original image.
1 is provided. The status display unit 59 has an LED (light emitting diode), and the received image data is held in the RAM 5 when there is an abnormality in the device or a user's erroneous operation, when the recording paper in the recording unit 10 runs out. When the automatic reception mode is set, the LEDs corresponding to error, paper supply, memory, and automatic reception are turned on to notify the user. Memory LED
When 62 is lit, by operating the memory print key 54, the image data stored in the RAM 5 is output from the recording unit 10 to the recording paper.

The density designating section 60 has a density designating key 63 and three LEDs 64, and the LED 64 is switched on each time the density designating key 63 is operated. The user specifies the density in three levels of dark, normal, and light according to the original image. When binarizing the output of the reading unit 1, the image processing unit 2 sets a threshold value corresponding to the stage specified here. As a result, the image data is appropriately binarized even if the image density varies from document to document.

The image quality designating section 61 has an image quality designating key 65 and five LEDs 66, and the LED 66 is switched on each time the image quality designating key 65 is operated. The user makes a selection according to the image quality of the document. That is, when the original image is a character image, normal, fine or super fine is designated. This determines the pixel density of the highest resolution layer. When the original image has halftone, halftone or super halftone is designated. The image processing unit 2 is provided with two types of dither matrices, and selects a matrix according to the designation here and performs dither processing, and binarizes the output of the reading unit 1.

The recording unit 10 employs a system in which an electrostatic latent image of an image is formed on the surface of a photosensitive drum, toner is attached to the electrostatic latent image to develop the image, and then the image is transferred to a recording sheet.

In the facsimile apparatus having the above structure,
All the image data read by the reading unit 1 and binarized by the image processing unit 2 are temporarily stored in the RAM 5.
The image data stored in the RAM 5 is read by the control unit 3, and the position of the adaptive template referred to when encoding is determined. The method of determining the adaptive template position will be described in detail later. In the progressive build-up, the image data stored in the RAM 5 is read by the control unit 3 to reduce the image, and the reduced image data is stored in the RAM 5.

At the time of transmission, information used for encoding the determined adaptive template position and selected model template is written in the header, modulated by the modem 7 and transmitted via the NCU 8. Then RAM5
The image data stored in is sequentially read and encoded by the encoding / decoding device 6 with reference to the model template and the adaptive template. The encoded image data is modulated by the modem 7, output from the NCU 8 to the telephone line, and transmitted to the receiving side.

On the other hand, the data received via the NCU 8 is first demodulated by the modem 7. A header is added to the beginning of the received data, and the control unit 3 reads out information at the time of encoding such as a model template and an adaptive template from the header. The encoding / decoding device 6 refers to these pieces of information and sequentially decodes the demodulated image data. As a result, the binary image data before being encoded by the transmission side device is reproduced. The binarized image data is immediately output to the recording paper by the recording unit 10 in the sequential buildup, once stored in the RAM 5 in the progressive buildup, and then by the operation of the memory print key 54 of the operation unit 9, or When the image with the highest resolution is reproduced, the recording unit 10 outputs the image on recording paper.

At the time of encoding, it is important to refer to a pixel having a strong correlation with the pixel to be encoded in order to improve the encoding efficiency. For example, in the case of a dither image, the image data has a correlation at a cycle corresponding to the size of the dither matrix used. That is, the number of pixels in the horizontal direction of the matrix in the horizontal direction (the x direction in FIGS. 8 and 9) and the number of pixels in the vertical direction of the matrix in the vertical direction (the same y direction) are set as one cycle, and the correlation between the pixel values is appear. In the facsimile apparatus of this embodiment, in order to improve the coding efficiency of image data, when the correlation period between pixels is known, the relative position of the adaptive template pixel to the coding pixel is changed within the range including the correlation period. , The image data is encoded for each adaptive template position to calculate the compression ratio, and the adaptive template pixel is determined at the position giving the highest compression ratio.

Specifically, the position of the adaptive template pixel is determined as follows. First, a known correlation period between pixels is input as the number of pixels ax in the horizontal direction (main scanning direction) and the number of pixels ay in the vertical direction (sub scanning direction) per period. A predetermined number of pixels bx and by are set in the horizontal and vertical directions, and the horizontal relative position k1 of the adaptive template pixel with respect to the encoded pixel,
The relative position k2 in the vertical direction is (ax-bx)-
(Ax + bx) and (ay-by) to (ay + by) are sequentially changed. The image data is encoded for all combinations of k1 and k2, and the compression rate C (k1, k2) is calculated according to the equation (1) for each encoding result.

Next, from the results of these encodings,
K which gives the highest compression rate, ie the compression rate with the smallest value
1, k2 is found, and the horizontal and vertical relative positions of the adaptive template pixel with respect to the coded pixel are determined. When the maximum compression ratio is obtained when both k1 and k2 are 0, the adaptive template pixel is set to the default position, for example, the position shown by A in FIGS. Further, even when the pixel numbers ax and ay are not input, the adaptive template pixel is set at the default position.

FIG. 3 shows a flow chart of the input processing of the pixel correlation period. After entering the adaptive template pixel input mode in step # 5, the pixel number ax in the x direction is input in step # 10, and the pixel number ay in the y direction is input in step # 15.
The pixel numbers ax and ay input in # 20 are stored in the RAM 5.

To input the correlation period, the AT key 67 (FIG. 2) provided on the operation unit 9 and the ten-key 5 described above are used.
1 and the setting key 58 are used. A specific example of the input operation is shown in FIG. FIG. 4 shows the display of the display panel 56 and the key operation performed by the user. Display panel 56 is usually D
1 is displayed, but the user is K1 and the AT key 6
By operating 7, the display is changed to D2, and the adaptive template pixel input mode is set.

When the setting key 58 is operated with K2, the display changes to D3, and when K3 is further operated,
The display of D4 is set, and the input waiting state for the number of pixels in the x direction is set. The user inputs a numerical value with the numeric keypad 51 with K4. If the number of pixels beside the dither matrix is 5,
At this time, enter 5. In response, the display changes to D5. If the entered value is incorrect,
Re-input using the cursor key 57 as described above.

Then, when K5 is operated, the display is changed to D6, and the input waiting state for the number of pixels in the y direction is set. The user inputs a numerical value with the numeric keypad 51 with K5. If the number of vertical pixels of the dither matrix is 7, then 7 is input at this time. In response, the display changes to D7. Further, by operating the setting key 58 with K7, the adaptive template pixel input mode is ended, and the display on the display panel 56 returns to the normal state as in D8.

FIG. 5 shows a flow chart of processing at the time of transmission. In step # 105, the number of pixels ax and ay representing the correlation period are read by the above-described method shown in FIGS. In step # 110, the document image is read by the reading unit 1, the image data is binarized for each pixel by the image processing unit 2, and the binarized image data is stored in the RAM 5. This operation is repeated until the reading of all pages of the document is completed.

At # 115, the positions ax and ay of the adaptive template pixels are read from the RAM 5 to the control unit 3, and the predetermined number of pixels bx in the horizontal direction and the number of predetermined pixels by in the vertical direction are by.
Is read from the ROM 4. At # 120, initial values ax-bx and ay-by are given to k1 and k2, respectively.

At # 125, the image data is encoded with reference to the adaptive template pixel whose relative position to the encoded pixel is determined by these k1 and k2. At this time, all the image data stored in the RAM 5 is read and encoded. Next, in # 130, the compression rate C (k1, k2) is calculated according to the equation (1), and k1, k2 are calculated.
It is also stored in the RAM 5 together.

In # 135, 1 is added to k2, and in # 140, k2
And ay + by. When k2 is equal to or less than ay + by, the process returns to # 125 to perform coding and compression rate calculation. By this iterative process, all compression rates for one k1 are calculated. When k2 exceeds ay + by, #
Proceeding to 145, 1 is added to k1 and k2 is returned to the initial value.

In step # 150, k1 and ax + bx are compared, and k1
Is less than or equal to ax + bx, the process returns to step # 130 to perform encoding and compression rate calculation. When k1 exceeds ax + bx, the process proceeds to # 155. At this stage, the adaptive template pixels are changed from (ax-1, ay-1) to (ax + 1,
The encoding and compression rate calculation set at the nine locations up to ay + 1) have all been completed.

At # 155, all the calculated compression rates and the corresponding k1 and k2 are read from the RAM 5. # 160
Then, these compression ratios are compared to find the minimum value, and the corresponding k1 and k2 are defined as the relative position of the adaptive template pixel with respect to the coded pixel. Next, at # 165, a header is created by transmitting from the other information ROM 4 such as a model template necessary for encoding, adding the adaptive template position, and transmitting the header.

Then, in # 170, the image data is read from the RAM 5 and encoded by the encoding / decoding device 6 with reference to the model template and the determined adaptive template. The coded image data is modulated by the modem 7 in # 175, output from the NCU 8 to the telephone line and transmitted.

Adaptive template pixels, whose relative position to the coded pixel is determined by the above method, are:
Since the correlation with the coded pixel is ensured, the coding efficiency is improved. In addition, since the adaptive template pixel is actually set at the position that gives the highest compression rate, the result of encoding at the time of transmission becomes a very high compression rate.

In this embodiment, all the image data is used to determine the positions of the adaptive template pixels, but only the image data in a smaller range, for example, the image data of the first page of the original is encoded and compressed. The rate may be calculated. In this case, the time required to determine the position of the adaptive template pixel can be shortened.

When a value close to the correlation period is input as the adaptive template pixel position, the relative position corresponding to the correct correlation period exists within the predetermined range for checking the compression ratio, which gives the highest compression ratio. .
Further, even when the original image is set to be tilted, even if some error occurs in reading the original image, the correlation period corresponding to the image data after reading exists within the predetermined range for checking the compression ratio. This gives the highest compression ratio. Therefore, even in these cases, encoding is performed at a high compression rate during transmission.

For this purpose, it is more effective to set the predetermined numbers of pixels bx and by to be large. However, b
If x and by are increased, the amount of encoding increases and the time required to determine the adaptive template pixel position increases, so the range of image data to be encoded is set small as described above.

Further, in the facsimile apparatus of the present embodiment, even when the correlation period is not known, the compression rate is checked not only at the input position but within a predetermined range including it, and the position giving the highest compression rate is checked. Since the adaptive template pixel is defined in, the compression rate can be surely increased.

Further, the default values of the pixel numbers ax and ay are stored in the ROM 4, and when the correlation period is unknown and these are not input, ax and ay are read from the ROM 4 to perform encoding and compression rate calculation. Alternatively, the adaptive template pixel position may be determined.

A predetermined number bx of pixels in the horizontal and vertical directions,
When each of the by values is set to 1 and the facsimile apparatus according to the present embodiment encodes various image data subjected to the dither processing, the compression rate according to the above equation (1) is 0.08 to 0.2. The result is obtained. As described above, according to this method, the binarized image data can be efficiently compressed.

The block diagram of FIG. 6 shows the configuration of an electronic copying machine according to the second embodiment of the present invention. The copying machine includes a scanner 31, an image processing unit 32, a printer 33, a control unit 34, an operation unit 35, an encoding / decoding unit 36, a transmission / reception unit 37, and a storage device 38. The original image is read by the scanner 31, and the image processing unit 3 operates on the read image data.
In step 2, shading, binarization and the like are performed, and the printer 33 outputs the recording sheet.

The control unit 34 controls the entire copying machine. The operation unit 35 includes various keys such as a numeric keypad,
By operating the keys of the operation unit 35, the user gives instructions to the control unit 34 such as recording paper size selection, number of copies, image enlargement / reduction, and image density setting. Further, the operation unit 35 has a display panel, and displays a message relating to the operation and an echo back display of the ten-key input to assist the operation of the user. The storage device 38 is provided outside the main body of the copying machine and is connected to the transmission / reception unit 37 via a data line 39. As a storage medium of the storage device 38, for example, R
AM, a magnetic disk or an optical disk is used.

The encoding / decoding unit 36 encodes the binarized image data according to the JBIG method. Transmitter / receiver 37
Outputs the image data encoded by the encoding / decoding unit 36 to the data line 39 and transmits it to the storage device 38. The storage device 38 stores and stores the received data. Further, the transmitting / receiving unit 37 receives the image data stored in the storage device 38 via the data line 39. The received data is decoded by the encoding / decoding unit 36.

The model template and the adaptive template are referred to when the image data is encoded by the encoding / decoding unit 36, and the positions of the adaptive template pixels are determined by the method shown in the first embodiment. That is, when the correlation period between pixels is known, the number of pixels corresponding to the horizontal and vertical correlation periods of the image data is input from the operation unit 35, and the position of the adaptive template pixel is set within a predetermined range including it. It is changed and encoded, and is set at the position that gives the highest compression rate. The positions of the selected model template and the determined adaptive template pixels are written in the header, stored in the storage device 38 together with the image data, and referred to by the encoding / decoding unit 36 at the time of decoding.

In the copying machine having the above-mentioned structure, the image data read by the scanner 31 and processed by the image processing unit 32 can be output to the recording paper by the printer 33, and can be encoded and stored in the storage device 38. You can also The user operates the keys of the operation unit 35 to select output to recording paper and storage in the storage device 38. Further, the image data stored in the storage device 38 is read out and output to the recording paper by the printer 33 at any time. This is also performed by the key operation of the operation unit 35.

Image data is coded at a high compression rate by performing coding with reference to the adaptive template pixel whose relative position to the coded pixel is determined by the method described above. Therefore, the transmitting / receiving unit 37 and the storage device 38
The transmission time of the image data during the period is shortened, the amount of data to be stored is reduced, and the physical storage area occupied by the image data in the storage device 38 is reduced.

Although the storage device 38 is installed outside the main body of the copying machine in this embodiment, the storage device 38 may be installed inside the main body of the copying machine. Further, the configuration excluding the printer 33 from the copying machine functions as an image scanner, and the present invention is also applicable to an image scanner.

[0071]

As described above, according to the present invention, in a communication device that encodes image data according to the JBIG encoding method, the adaptive template pixel is changed within a predetermined range including the input position, and each position is changed. Since the image data is encoded to calculate the compression ratio and finds the position that gives the highest compression ratio, if the image data has a known correlation cycle, input the position corresponding to that cycle to ensure In addition, it is possible to encode at an extremely high compression rate.

Further, when the input position is a value which does not completely match and is close to the correlation period of the image data, or when there is some error in reading the original image, such as when the original is tilted and read. Even if there is, the compression rate is calculated even in the vicinity of the input position, so that the above effect is exhibited.

Further, even when the correlation period is not known, the position of the adaptive template pixel that gives the maximum compression ratio within the predetermined range including the input position is found, so that the coding efficiency is certainly improved.

According to the structure of claim 2, in a communication device for transmitting by encoding the image data composed of binarized pixels by sequentially encoding the values of each pixel,
Since the position of the reference pixel with respect to the pixel to be coded is changed within a predetermined size range including the number of input pixels and the compression rate is calculated by performing coding at each reference pixel position, image data When the correlation period of is known,
By inputting the number of vertical and horizontal pixels corresponding to the one period, the image data can be reliably encoded with an extremely high compression rate.

Even when the number of input pixels is slightly different from the correlation period of the image data, or when there is some error in reading the original image, such as when the original is tilted and read, the input is made. Since the encoding and the compression rate calculation are performed also at the positions around the number of pixels, the above effect is exhibited.

Further, even when the correlation cycle is not known, the compression rate is calculated by setting the reference pixel not only at the position corresponding to the input pixel number but also at the peripheral position thereof, so that a high compression rate is obtained. The reference pixel location that gives the rate is found. Therefore, the compression rate of the image data is surely improved.

In the facsimile apparatus according to the third aspect, when the correlation period of the pixel is known, the value corresponding to the period is input so that the transmission side device can encode the image data at an extremely high compression rate. it can. Therefore,
The time for transmitting the image data from the transmission side device to the reception side device is shortened, and the transmission efficiency is improved. Even if the correlation period is unknown, the compression rate is increased, so that the transmission efficiency is surely improved.

Further, even when the copying machine according to claim 4 and the image scanner according to claim 5 are used, when the correlation period of the pixel is known, the number of the period pixels is input, so that the code of the image data can be coded at an extremely high compression rate. Can be converted. Therefore, the transmission time of the image data to the storage device is shortened and the storage area of the storage device required to store the image data is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a facsimile apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an appearance of an operation unit of the facsimile apparatus according to the first embodiment.

FIG. 3 is a flowchart of a process of inputting the number of pixels in a correlation cycle according to the first embodiment.

FIG. 4 is a diagram showing a display on a display unit and a user's key operation when inputting the number of pixels in a correlation cycle according to the first embodiment.

FIG. 5 is a flowchart showing a process at the time of transmission of the facsimile apparatus of the first embodiment.

FIG. 6 is a block diagram showing a configuration of an electronic copying machine according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing an outline of a JBIG base system.

FIG. 8 is a diagram showing default positions of a two-line model template and an adaptive template of an image of a lowest resolution layer.

FIG. 9 is a diagram showing default positions of a 3-line model template and an adaptive template of an image of the lowest resolution layer.

[Explanation of symbols]

 1 reading unit 2 image processing unit 3 control unit 4 ROM 5 RAM 6 encoding / decoding device 7 modem 8 NCU 9 operation unit 10 recording unit

Claims (5)

[Claims] 1. A communication device for encoding image data according to the JBIG encoding method, input means for inputting positions of adaptive template pixels, and size of image data before encoding and image data after encoding. And a compression ratio calculation unit for calculating a compression ratio by encoding, and changing the position of the adaptive template pixel within a predetermined range including the position input from the input unit, and encoding the image data at each position. Then, the compression ratio is calculated by the compression ratio calculation unit, and the position determination unit that determines the position of the adaptive template pixel that gives the highest compression ratio, and the adaptive template pixel whose position is determined by the position determination unit are referred to. And a coding means for coding the image data. 2. In a communication device for transmitting image data composed of binarized pixels by sequentially encoding the values of each pixel and transmitting the same, the number of horizontal pixels and the number of vertical pixels are input. Input means for encoding, encoding means for sequentially encoding the encoding target pixels by referring to reference pixels at a predetermined relative position to the encoding target pixels, and encoding the image data, and A compression ratio calculation unit that calculates the compression ratio by encoding by comparing the size of the image data and the size of the image data after encoding, the relative position of the reference pixel with respect to the pixel to be encoded, the horizontal direction in the horizontal direction. The number of pixels is changed within a range of a first predetermined number of pixels, and each horizontal position is changed in the vertical direction within a range of a second predetermined number of pixels including the number of pixels in the vertical direction. With respect to the encoding means Image data is encoded, the compression rate is calculated by the compression rate calculating means, the position giving the highest compression rate is found, and this position is determined as the relative position of the reference pixel with respect to the encoding target pixel. And a communication device. 3. The communication device according to claim 1 or 2 is a facsimile device. 4. The communication apparatus according to claim 1, wherein the document reading unit and the image processing unit that processes the image data read by the document reading unit and provides the image data to the encoding unit. And a transmission means for transmitting the image data encoded by the encoding means to a storage device. 5. The communication device according to claim 1 or 2, wherein an original reading unit and an image processing unit that processes the image data read by the original reading unit and provides the image data to the encoding unit. And a transmission means for transmitting the image data encoded by the encoding means to a storage device.